Rapid Part Qualification Methodology of Aircraft Metallic Components using Direct Digital Manufacturing Technologies

The Phase II objective is to demonstrate the vision that the reuse of knowledge gained from known designs for Direct Digital Manufacturing (DDM) of building blocks in a laboratory can be leveraged in order to produce and rapidly qualify complex DDM parts whose geometry can be expressed as union of building block geometries. The DDM of such a part will be designed using a heuristic and adaptive analytical framework that seeks thermal and flow similitude between the building block deposit and the part deposit, instead of a rigorous computational simulation-based design. The various elements of this framework are designed to overcome the technical barriers in qualification that arise from the approval of deposition and geometry parameters, and the determination of probability of detection (POD) of defects. It allows for the evaluation of DDM equipment capability for the deposition of fine features, which is also beneficial for the comparative evaluation of two machines for the deposition of the same part. The framework has been designed to minimize the effort in the collection of knowledge based on the building block DDM, its reuse for part DDM, and nondestructive inspection. Dimensionless metric parameters will be designed in order to overcome the dependence of part quality on the size, sequence and orientation of the deposit build. The admissible window for the dimensionless metric parameters will be defined based on the in-process temperature data for the building block. The POD of defects will be calculated by performing building block deposits within the admissible window of processing parameters and its vicinity. The process parameters for the part deposition will be controlled using a feedback loop that will seek to maintain the process within a subset of the admissible window in order to provide a margin of safety. Excursion of the material thermo-mechanical path outside the admissible window will be mapped to the POD data and a part-specific inspection plan will be generated. The part will be subject to NDI, evaluation of microstructure heterogeneity on local mechanical properties, and limited mechanical tests for tension, fatigue and fracture toughness. The admissible window, POD, feedback control data, inspection plan, NDI and mechanical tests will comprise a data package that is deemed to reduce the qualification effort. This data package will be documented in the form of a part-specific process qualification record (PQR) and the DDM process will be documented as a draft DDM process specification (DPS). The technology will be demonstrated for powder spray and powder bed DDM.